261665603554 has 8 divisors (see below), whose sum is σ = 392507479980. Its totient is φ = 130829776896.

The previous prime is 261665603509. The next prime is 261665603561. The reversal of 261665603554 is 455306566162.

It can be written as a sum of positive squares in 2 ways, for example, as 261126110025 + 539493529 = 511005^2 + 23227^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a junction number, because it is equal to n+sod(n) for n = 261665603498 and 261665603507.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1402719 + ... + 1578274.

Almost surely, 2^261665603554 is an apocalyptic number.

261665603554 is a deficient number, since it is larger than the sum of its proper divisors (130841876426).

261665603554 is a wasteful number, since it uses less digits than its factorization.

261665603554 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3024884.

The product of its (nonzero) digits is 3888000, while the sum is 49.

The spelling of 261665603554 in words is "two hundred sixty-one billion, six hundred sixty-five million, six hundred three thousand, five hundred fifty-four".